Investigation of the potential of green tea in inducing browning in vitro in pre-adipocytes and in the subcutaneous adipose tissue from obese adiponectin knockout mice

Abstract

Obesity is currently a challenge for the health system worldwide as it is a risk factor for numerous diseases with high comorbidity. Associated with sedentarism and a food imbalance due to the intake of hypercaloric foods with reduced nutrient content, the number of people with obesity and overweight has been increasing in the last decades. The great fat and energy deposit is adipose tissue (TA), which has several characteristics and acts as a regulator of metabolic homeostasis and body thermogenesis. TA can be classified as white adipose tissue (BAD) and brown adipose tissue (TAM). The TAB cells have a single lipid droplet, and its cytoplasm is barely visible, its main function is to store energy in the form of triglycerides (lipogenesis) and release their stocks when performing lipolysis. TAM is characterized by the presence of numerous lipid droplets and expression of the proton uncoupling protein 1 (UCP-1) whose main function is thermogenesis without tremor. Recently, a variation of BAD, called adipose tissue beige/"brite" was discovered. The adipocytes of this tissue have characteristics of the TAM, since they express UCP-1 and perform the thermogenesis with consequent energy expenditure. The subcutaneous TAB undergoes this variation in beige by different stimuli, among them the exposure to the cold, signaling via ²3 adrenergic receptors, in a process called browning. Adiponectin is an important means to induce browning in the subcutaneous TAB and data from our research group found that adiponectin levels that were reduced in the plasma of obese animals were restored after treatment with green tea. In addition, our laboratory studies evaluating the gene expression of some browning markers in subcutaneous RT and the TAM thermogenic pathway of obese animals treated with green tea showed that the treatment induced increased expression of several thermogenic marker genes related to mitochondria and The oxidation of AG. Therefore, we assume that knockout mice for adiponectin (AdipoKO) and fed a high fat diet (HFD) and treated with green tea will not significantly increase beige TA, as these animals will be refractory to the effects of green tea, since the actions of green tea In our hypothesis are mediated by adiponectin. To investigate the mechanisms involved our general objective is to ascertain in vivo the role of adiponectin in knockout mice for this protein (AdipoKO) exposed to a HFD and treated with green tea. For this purpose, the animals will receive HFD for 4 weeks and after that period, we will start the gavage with green tea extract (500 mg/kg) for 12 weeks in addition to the hyperlipid diet. Subsequently the animals will be euthanized to obtain the subcutaneous TAB. The total TABsc RNA will be extracted through the use of tri-reagent and subsequent real-time PCR (Polymerase Chain Reaction) for evaluation of browning marker genes (UCP1, PGC1-±, Sirt1, CD36, B3 receptors, Dio2, PRDM16, Cidea, TMEM-26, tyrosine hydroxylase (TH), GLUT4, Fas, ACC, PPAR g and ±); And in vitro the effect of green tea polyphenols on the differentiation and identity of 3T3F442A adipocytes. Through this study, we intend to contribute to the understanding of the role of adiponectin in subcutaneous RT and the crucial role of green tea in the fight against obesity. (AU)